Recovery of fuel from oil shale

Abstract

Raw shale is supplied to a pyrolyzer where it is pyrolyzed by fuel gas and hot spent shale derived from a gasifier. Typically, the raw shale is Eastern U.S. shale and the pyrolyzer includes a fluidized bed. The pyrolyzed shale having given up its oil and volatile hydrocarbons, rises to the top of the fluidized bed of raw shale where it is transferred to the gasifier. Oxygen and steam are supplied to the gasifier. This composite gas reacts with the carbon of the pyrolyzed shale in a fluidized bed to produce synthesis or fuel gas. The oxygen is supplied in such quantities as not to react completely with the carbon in the pyrolyzed shale. The steam reacts with the excess of carbon. Predominantly hydrogen and carbon monoxide are produced; in addition there is a smaller quantity of carbon dioxide and methane. This hot fuel gas is transferred to the pyrolyzer. In addition, hot spent shale is transferred to the pyrolyzer. The hot fuel gas fluidizes the raw shale in the pyrolyzer. The hot gas and the hot spent shale heat the raw shale separating the shale oil and product gas including volatile hydrocarbons. The oil is condensed and collected, the fuel gas is collected for utilization in the above process and also for other purposes.

We claim: 
     
       1. The method of recovering fuel from oil shale with apparatus including a pyrolyzer and a gasifier, wherein a stream of particles of raw shale is fed into the pyrolyzer and is to be heated in said pyrolyzer to thereby produce shale oil, product gas, including volatile compounds from said shale, and pyrolyzed shale containing residual carbon, the said method comprising supplying to said gasifier gas including oxygen and steam, transferring said pyrolyzed shale from said pyrolyzer to said gasifier, passing said gas in said gasifier through said pyrolyzed shale, to produce a fluidized bed of said pyrolyzed shale, reacting said oxygen and steam chemically with said pyrolyzed shale in said fluidized bed in said gasifier to produce hot fuel gas and hot spent shale, the quantity of oxygen supplied being substantially less than that required to react completely with said residual carbon contained in said pyrolyzed shale and the quantity of steam supplied being sufficient to react with substantially the remainder of said residual carbon whereby said fuel gas is produced, transmitting said hot fuel gas to said pyrolyzer, passing said hot fuel gas through said raw shale at the bottom of said fluidized bed to produce a fluidized bed of said raw shale, contacting said hot fuel gas with said raw shale in said fluidized bed in said pyrolyzer thermally to heat said raw shale, the heating of said raw shale by said hot fuel gas separating said oil and product gas from said raw shale, transmitting said product gas and fuel gas resulting from the reaction of the steam and oxygen with said residual carbon from said pyrolyzer to a facility for separating said product gas as a fuel, and collecting the oil separated from said raw shale. 
     
     
       2. The method of claim 1 wherein the oil separated from the raw shale in the pyrolyzer is vaporized and the vapor from said oil is condensed and collected. 
     
     
       3. The method of claim 1 wherein the raw shale is preheated before it is fed into the pyrolyzer, the said raw shale being preheated by heat derived from the spent shale and carried by fuel gas derived from the facility. 
     
     
       4. The method of claim 1 wherein the heat for preheating the oxygen in the gas containing the oxygen and the steam and the heat for producing the steam in said gas is at least in part derived from fuel gas transmitted from the facility. 
     
     
       5. The method of claim 1 including transmitting the hot spent shale from the gasifier to the pyrolyzer and contacting the said hot spent shale thermally with the raw shale in said pyrolyzer to heat said raw shale additionally, the said heating of said raw shale contributing to the separation of the oil and volatile compounds from said raw shale. 
     
     
       6. The method of recovering fuel from raw oil shale with apparatus including a pyrolyzer and a gasifier, wherein a stream of particled raw shale is fed into the pyrolyzer and is to be heated in aid pyrolyzer to thereby produce shale oil and product gas, including volatile compounds from said shale, and pyrolyzed shale containing carbon and wherein said pyrolyzed shale is thereafter to be transferred to said gasifier, the said method comprising supplying to said gasifier gas including oxygen and steam, passing said gas in said gasifier through said pyrolyzed shale to produce a fluidized bed of said pyrolyzed shale, said pyrolyzed shale including residual carbon, reacting said oxygen and steam chemically with said carbon in said pyrolyzed shale in said gasifier to produce hot fuel gas and hot spent shale, the quantities of oxygen and steam being so related that said residual carbon is efficiently converted into fuel gas, passing said hot gas through said raw shale to produce a fluidized bed of said raw shale in said pyrolyzer, transferring pyrolyzed shale from the region at or near the top of said fluidized bed of raw shale in said pyrolyzer to said gasifier as the pyrolyzed shale in said gasifier, reacting said hot fuel gas thermally with said raw shale in said fluidized bed in said pyrolyzer to heat said raw shale, transferring said hot spent shale together with said gas from said gasifier to said pyrolyzer through the region at or near the bottom of the fluidized bed of raw shale in said pyrolyzer to heat said raw shale additionally, the heating of said raw shale, by said hot fuel gas and by said hot pyrolyzed shale producing product gas and oil, transmitting said product gas from said pyrolyzer to a facility for utilizing said product gas, and collecting the oil separated from said raw shale. 
     
     
       7. The method of claim 1 wherein the reaction of the oxygen and the residual carbon is exothermic and the reaction of the steam and the remainder of the residual carbon is endothermic, the endothermic reaction absorbing heat from the exothermic reaction of the residual carbon and the oxygen to maintain the temperature of the raw shale below a magnitude at which the oil in the shale is cracked. 
     
     
       8. The method of claim 1 wherein the pyrolyzer is maintained at a temperature between 700° F. and 1200° F. and at a pressure between 30 psig and 50 psig and the gasifier is maintained at a temperature between 1400° F. and 1800° F. and at a pressure between 30 psig and 50 psig. 
     
     
       9. The method of claim 6 wherein the reaction of the oxygen and the residual carbon is exothermic and the reaction of the stream and the remainder of the residual carbon is endothermic, the endothermic reaction absorbing heat from the exothermic reaction of the residual carbon and the oxygen to maintain the temperature of the raw shale below a magnitude at which the oil in the shale is cracked. 
     
     
       10. The method of claim 6 wherein the pyrolyzer is maintained at a temperature between 700° F. and 1200° F. and at a pressure between 30 psig and 50 psig and the gasifier is maintained at a temperature between 1400° F. and 1800° F. and at a pressure between 30 psig and 50 psig.